Heater



FIG. 1 is a top perspective view of a heater showing our new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a right side elevation view thereof;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a left side elevation view thereof; and,

FIG. 6 is a rear elevation view thereof.

The subject matter shown in broken lines forms no part of the claimed design. 

The ornamental design for a heater, as shown and described. 